Robber‐like pollinators: overwintered queen bumblebees foraging on Corydalis ambigua

Abstract

1. The behaviour of nectar-collecting Bombus hypocritu sapporensis Cockerell queens was observed on a population of a spring ephemeral plant Corydulis umbiguu Cham. et Schlecht.2. Daily patterns of activity and behaviour changed with the progress of flowering. Activity peaked shortly before sunset early in the flowering season but approximately at noon towards the end of flowering. In the peak flowering period the queens tended to visit nearby plants and to change direction often, whereas early or late in the flowering period they flew further between visits and were less likely to change direction.3. Each plant was visited 0 to 24 times (mean 9.4 +SD 5.2) by the queens during the whole flowering season.4. The queens collected nectar, rarely through the front of the flowers but mostly through the spurs perforated by themselves or predecessors. At the beginning of the flowering season the illegitimate foragers often visited the front of the flowers before moving to the spurs; later, most queens quickly learned to land directly on the spurs. 5. Even the 59.7% of plants that were visited only by illegitimate foragers set seeds. Close observation confirmed that the illegitimate foragers opened the inner petals enclosing anthers and stigma frequently when visiting the front of the flowers before robbing, or occasionally when walking about on the flowers or collecting nectar through the perforated spurs.

Alien Bumble Bee Affects Native Plant Reproduction Through Interactions With Native Bumble Bees

“…Legitimate B. ardens always insert their proboscis into the spur from the flower entrance and suck the nectar. In contrast, B. hypocrita and B. terrestris have the large mandibles and thick proboscis, thereby they invariably bite holes at the spur of C. ambigua from the top or side of the flower, and rob nectar (Higashi et al 1988, Ito 1991, Kudo et al 2001, Kudo and Kasagi 2004, Matsumura et al 2004, Kenta et al 2007; J. Yokoyama and I. Dohzono, unpublished data). At our study sites, other bumble bee species (B. diversus, B. hypnorum, and B. schrencki), the bombylid fly (Bombylius sp.…”

“…Corydalis ambigua is a very common spring ephemeral in northern Japan, and the flowers of this species are tubular and rely on native bumble bee species for pollination (Higashi et al 1988, Kudo et al 2001, Kudo and Kasagi 2004. In addition, the nectar and pollen of C. ambigua are important nutrient sources for native bumble bee queens that begin nesting after hibernation.…”

“…4). Previous studies indicated that although B. hypocrita and B. terrestris rob nectar by perforating spurs (Ohara and Higashi 1994, Kudo et al 2001, Kudo and Kasagi 2004, the former species sometimes accidentally opens petals and picks up pollen while robbing, which can contribute to fertilization (robberlike pollination; Higashi et al 1988). In some areas in Hokkaido, Japan, C. ambigua is pollinated primarily by B. hypocrita, and floral sex allocation has been altered to improve pollen flow (Kudo and Kasagi 2004).…”

Nectar thieves influence reproductive fitness by altering behaviour of nectar robbers and legitimate pollinators in Corydalis ambigua (Fumariaceae)

“…For example, when larger bumblebees visit a Corydalis flower, their abdomens typically touch the floral sexual organs and accomplish pollination. Higashi et al (1988) termed such nectar robbers that could pollinate as 'robberlike pollinators'. However, sometimes, nectar robbers, legitimate pollinators and other illegitimate visitors may be present together in a complex pollination system.…”

“…Nectar robbing in Corydalis has been widely described in North America and East Asia (Ohara & Higashi 1994;Maloof 2001;Zhang et al 2009a), and its fecundity can be strongly affected by such visits (Sakagami 1951;Higashi et al 1988;Ohara & Higashi 1994;Kudo, Maeda & Narita 2001). We conducted an investigation of a complex pollination system involving the Asian species Corydalis ambigua, consisting of legitimate floral visitors (i.e.…”